Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41g mL-1 and the mass percent of nitric acid in it being 69%.

The correct option/answer is 15.44 mol/L.

To calculate the concentration of nitric acid (HNO₃) in moles per litre (molarity), we can follow a step-by-step approach starting from the definition of mass percent and density.

Step 1: Understand the given data
- Mass percent of nitric acid (HNO₃) = 69%
- Density of the nitric acid solution ($d$) = 1.41 g mL^-1
- Molar mass of nitric acid (HNO₃):
$\text{Molar mass of}{\mathrm{HNO}}_3=1\text{(for H)}+14\text{(for N)}+3\times 16\text{(for O)}=1+14+48=63\text{g/mol}$

Step 2: Find the mass of nitric acid in a given volume of solution
Let us consider 1 Litre (1000 mL) of the nitric acid solution.
Using the density formula:
$\text{Mass of solution}=\text{Volume}\times \text{Density}$
$\text{Mass of 1000 mL solution}=1000\text{mL}\times 1.41\text{g/mL}=1410\text{g}$

Since the solution contains 69% nitric acid by mass, the mass of pure HNO₃ in this solution is:
$\text{Mass of}{\mathrm{HNO}}_3=1410\text{g}\times \frac{69}{100}=972.9\text{g}$

Step 3: Calculate the number of moles of nitric acid
The number of moles ($n$) is given by the ratio of mass to molar mass:
$\mathrm{Moles\; of}{\mathrm{HNO}}_3=\frac{972.9\text{g}}{63\text{g/mol}}\approx 15.44\text{moles}$

Step 4: Determine the concentration (molarity)
Molarity is defined as the number of moles of solute dissolved in 1 Litre of solution:
$\text{Molarity}=\frac{\text{Moles of solute}}{\text{Volume of solution in Litres}}$
Since we assumed a volume of 1 Litre of solution, the molarity is:
$\text{Concentration}=\frac{15.44\text{moles}}{1\text{L}}=15.44\text{mol/L}$

Thus, the concentration of nitric acid is 15.44 mol/L.